Jet-driven outflows in Seyfert galaxies .

Abstract

Growing evidence over the past decade has indicated that low-luminosity active galaxies are often associated with outflows from their nuclei. In particular, a small but important fraction of Seyfert galaxies have extended collimated radio emission on the scales of the narrow-line region (NLR). In most of these cases, the emission-line gas displays morphological and kinematic signatures of disturbance or acceleration by the nuclear jet. Using the STIS spectrograph on the HST, we have obtained high spatial resolution long-slit spectra of six Seyfert galaxies which show clear signs of jet-gas interactions. Combined with HST and ground-based optical and archival radio imaging, we are able to explore these interactions in considerable detail. We have isolated the signatures of a number of key dynamical processes such as cloud shocks and acceleration, ablation, jet bending and drag forces. Other elements of the circumnuclear environment, such as gaseous disks, AGN winds and star-forming regions are also shown to play an important role in our view and interpretation of jet interaction and Seyfert ionization. Finally, a detailed dynamical study of jet-interaction archetype Mkn 78 provides strong evidence for a thermally-dominated, slow and dense Seyfert jet, quite unlike the powerful jets thought to be present in classical Radio Galaxies. Our results provide new insights into the nature of nuclear outflows in low-luminosity and radio-quiet AGN.